1. Field of the Invention
The present invention relates to a mobile communication system, and more particularly, to an apparatus and a method for allocating frequency resources in a mobile communication system.
2. Description of the Related Art
The Institute of Electrical and Electronics Engineers (IEEE) 802.16 d/e communication system is a broadband wireless access communication system which enables high speed/large capacity communication for mobile stations by using sub-carriers or sub-channels which are frequency resources orthogonal to each other. Schemes used for the high speed/large capacity communication include a Band Adaptive Modulation and Coding (Band AMC) scheme.
The Band AMC scheme refers to a modulation and coding scheme which adaptively changes according to channel conditions of a base station. For example, according to the Band AMC scheme, a base station uses a higher-order modulation scheme and a lower-order coding scheme for a mobile station having a relatively good channel condition, in order to improve the transmission efficiency, and transmits data by using a lower-order modulation scheme and a higher-order coding scheme for a mobile station having a relatively poor channel condition. In other words, the Band AMC scheme employs an optimum modulation scheme and an optimum coding scheme based on the channel condition of a mobile station. Therefore, by the Band AMC scheme, it is possible to actively account for the channel environment and effectively use the frequency resources.
Meanwhile, in view of the frame structure of the broadband wireless access communication system, the sub-channels of the system can be divided into diversity sub-channels and Band AMC sub-channels. The diversity sub-channels are allocated to mobile stations in relatively poor channel conditions and the Band AMC sub-channels are allocated to mobile stations in relatively good channel conditions. However, the current IEEE 802.16 d/e standards have yet to present any specific sub-channel allocation scheme.